Fix: Natural Language Search Error on Complex Queries

## What would you like to be added?
Natural language search returns 500 error when handling complex queries. Simple queries (e.g., 'What are the resources containing demo?') work fine, but complex queries (e.g., 'Which pods are in error state') trigger server errors.


## Why is this needed?
This fix is crucial for improving user experience. The current error impacts the core functionality of using natural language for resource queries, especially for state-related searches.

Required improvements:
1. Enhance natural language processing robustness
3. Improve error handling mechanism
3. Support more complex query patterns
4. Add comprehensive test cases

Steps to reproduce:
1. Go to search page
2. Try query 'Which pods are in error state'
3. Observe 500 error response

Expected behavior:
- Should return a list of pods in error state
- Should handle complex state queries gracefully

Start at the search page and reproduce the failing query “Which pods are in error state,” then compare its server response with the working resource query. Trace where the complex query produces the 500 error, add coverage for state-related and other complex queries, and verify that the request returns the expected pod list without a server error.

Written by the indexing model from the issue text.